CucumberCucumis sativus

The cucumber wants constant warmth, even more than the tomato. In Belgium, a greenhouse, polytunnel or tall cold frame are its best allies; failing that, give it the foot of a south-facing wall, sheltered from cool winds, where heat builds up in the afternoon. Plan from the outset to grow it vertically on a trellis or netting: it takes up less room, airs the foliage and gives straight fruit. Avoid the spot where last year's courgettes, melons or squashes grew, as they share its diseases. In a greenhouse, keep it away from the tomatoes: it likes a more humid atmosphere than they do.

Two to three weeks before planting, open up a hole thirty centimetres in every direction for each plant and fill it with equal parts soil and mature compost, forming a small mound. The gentle fermentation of the compost warms the soil, which the cucumber particularly appreciates. In clay soil, lighten with coarse sand or leaf mould: the cucumber's shallow roots suffocate in compacted, waterlogged ground. A black film or dark mulch laid ten days before planting gains a few precious degrees in the soil.

Sow between 20 April and 10 May for growing under cover, around 5 May for outdoors. The seed needs 22 to 25 °C to germinate: stand the pots on a radiator, in an indoor propagator or on a heat mat, and take them off the heat as soon as they come up to avoid legginess. So-called parthenocarpic varieties, free of bitterness, fruit without pollination and are perfectly suited to the greenhouse. Outdoors, prefer a short cucumber or a gherkin, which are more tolerant. A second sowing in late June, planted out in July, takes over when the first plants tire in September.

Plant out a young plant with two or three true leaves, never an older one that has already begun to trail. Remove it from its pot carefully, keeping the root ball intact, set it on the prepared mound with the neck slightly raised, and water with tepid water. In a greenhouse, plant from mid-May; outdoors, wait until late May and put a cloche or fleece over it for the first week. Fix the string or trellis straight away, then guide the stem by winding it gently clockwise. Protect the neck from slugs, which are very fond of young plants.

A cucumber in a pot on a warm balcony easily gives a dozen fruits. Choose a container of twenty-five to thirty litres, potting compost enriched with a third of garden compost, and a sturdy support fixed to the wall or railing: the plant climbs to two metres. Compact varieties, often sold for balconies, are content with a fifteen-litre pot. The ideal aspect is south or south-west, sheltered from wind, which dries out the foliage. The compost must stay moist at all times: in July, water every morning with tepid water and use a saucer. A liquid feed every ten days keeps production going.

Sowing in early April and ending up with a tangled fifty-centimetre plant that never recovers. Planting into soil at 12 °C: the cucumber sulks, yellows and gets eaten by slugs. Watering with cold water from the hose, which causes a shock and makes the fruit bitter. Letting a plant that should climb sprawl on the ground, with twisted, rotten fruit as the result. Growing ordinary and parthenocarpic cucumbers side by side in the greenhouse, which gives fruit swollen with seeds. Leaving a fruit to yellow on the plant, which stops the next ones from forming.

The cucumber drinks a lot and often. Water at the base, with water that is not ice-cold, every two days in hot weather, every day in a greenhouse in full production, giving three to five litres per plant. Regularity matters more than quantity: soil that dries out and then gets sodden produces bitter, pinched or hollow fruit. A drip line or an upturned bottle works wonders. In a greenhouse, water the paths too and mist the foliage in the morning during hot spells to keep up the ambient humidity that deters red spider mite. Avoid wetting the leaves in the evening, though.

Mulch from planting in the greenhouse, and as soon as the soil has warmed outdoors, with five to eight centimetres of straw or dried grass clippings. On a terrace, a hemp or flax mulch does just as well. The cucumber produces fast and quickly exhausts its reserves: give nettle liquid diluted to 10 % every fortnight at the start of the season, then comfrey liquid or an organic feed rich in potash from the first fruits. A ring of mature compost laid around the base in July revives a flagging plant. Avoid excess nitrogen feeds; they make the fruit watery.

Train the main stem up its support by winding it around the string each week or tying it to the trellis with a soft tie. Remove flowers and side shoots on the first forty centimetres so the plant can settle in. Above that, cut back the side stems after the second leaf beyond a fruit; this balances growth and production. When the main stem reaches the ridge of the greenhouse or the top of the support, cut off its tip: the side branches take over. Remove yellowed lower leaves and misshapen fruit, which draw sap for nothing. On ordinary varieties, do not remove the male flowers.

In a greenhouse, powdery mildew and red spider mite are the two scourges of summer. Ventilate generously every day from 20 °C, mist in hot spells, water the paths and space the plants out: dry, stuffy air opens the door to them. Spray milk diluted to 10 % or a horsetail decoction at the first white spots. Against red spider mite, a shower over the foliage in the morning and soft soap on the undersides of the leaves. Aphids are drowned with diluted soft soap. A plant that wilts suddenly is often suffering from stem rot at the neck: water away from the stem and raise the mound higher the following year.

Late April: sowing in warmth on a radiator. Mid-May: planting in the greenhouse with string and mulch; late May outdoors under a cloche. June: weekly training, removal of low shoots, nettle liquid, first daily watering in hot weather. Late June: second sowing for the relay. July: harvest every two days, daily ventilation of the greenhouse, misting, comfrey liquid, watching for red spider mite. August: pinching out the tip at the ridge, milk sprays against powdery mildew, planting out the relay plants. September: the young plants produce until the first cold snaps. October: pulling up, cleaning and disinfecting the supports.

Harvest early in the morning, with a knife, never pulling on the stem, as soon as the fruit is full-sized and the skin is still good and green and firm. In a greenhouse, picking is almost daily in July and August. A forgotten fruit yellows, fills with seeds and tells the plant to stop: remove it without regret. The relay sowing planted in July extends the harvest into October, especially under cover. During the first cool nights, close the greenhouse in the evening and cover outdoor plants with fleece. Gherkins are picked daily at four or five centimetres, which keeps them producing endlessly.